Revit Guides
Data Management
ELI5
Electrical & Mechanical Equipment: Access & Maintenance (UK)
TL;DR
There is no universal “1 m rule” in UK law or BS 7671. The legal duty is to provide adequate working space, access and lighting (EAWR Reg. 15). Legislation.gov.uk
Numbers appear when you’re in restricted-access electrical rooms (BS 7671 Section 729: operating/maintenance gangways) and from manufacturer instructions. electrical.theiet.org+1
Some sectors/clients (e.g., UK water industry via WIMES) do require ~1 m clearance — that’s client/sector spec, not law. pumpcentre.com+1
1. What the law actually requires (baseline for every project)
EAWR Reg. 15: provide adequate working space, adequate means of access and adequate lighting at electrical equipment where work may give rise to danger. This is your non-negotiable legal anchor for layouts and clearances. Legislation.gov.uk
CDM 2015 (designer duty): design to eliminate, reduce or control foreseeable risks; provide enough information with the design so others can comply. (Use this to justify room sizing, door swing, heavy-item removal routes, etc.) Legislation.gov.ukHSE
HSG85: practical HSE guidance on safe working around electrical gear (planning, safe access/space, lighting). Use it to evidence your maintenance reasoning alongside EAWR. HSEhealthandsafety-services.co.uk
Fire service access overlay (ADB B5): coordinate plant room locations and external access with the vehicle access rules (e.g., a door every ≤ 60 m on accessible elevations; min 750 mm door width). GOV.UK
2. When BS 7671 gives you actual numbers
In restricted-access electrical rooms (e.g., switchrooms, locked plant areas/roofs reserved for skilled/instructed persons), BS 7671 Section 729 sets minimum gangway/working-space envelopes and related conditions for operation and maintenance. Typical design outcomes include:
Baseline gangway (barriers/enclosures as basic protection)
– Working width around ≥ 700 mm
– Headroom around ≥ 2000 mm
– Keep live parts out of normal reach (often taken as ≥ 2500 mm).Encroachment while doors are open / withdrawable gear
– Preserve a passing width during maintenance, keep safe door swing (≥ 90°) and working depth at fronts.Long line-ups, exits & doors
– Long gangways should be accessible from both ends (triggered around 10–20 m depending on room geometry and dooring); doors/hinged panels to open ≥ 90°.
These are BS 7671 figures/conditions specific to restricted areas. Always check the current edition (and any manufacturer overlay). electrical.theiet.org+1
If protective measure is barriers/enclosures → 700 mm / 2000 mm / 2500 mm.
If unprotected live parts (one side) → 900 mm gangway; 700 mm in front of controls; 2500 mm to live parts.
If live parts on both sides → 1300 mm between live parts; 1100 mm min from handle to opposite live parts; 900 mm free in front of controls; 2500 mm to live parts. Iteh Standards
Restricted vs. open‑access context (who the room is for)
Restricted access areas must be signed and kept locked to skilled or instructed persons only; unauthorised persons must not have access. (This is the premise for applying Section 729 numbers to panel/DB rooms.) Iteh Standards
End wall clearance for long runs
For long line‑ups, place equipment a minimum of 700 mm from end walls (or provide a second door) so gangways > 10 m are accessible from both ends. Closed restricted‑access areas > 20 m must have doors at both ends. Iteh Standards
Isolation & emergency switching (applies to all panels/DBs)
Ensure suitable means are available for cutting off the supply and for isolation; “isolation” means secure disconnection and separation from every source of electrical energy. (Position, labelling and access to these devices must reflect the EAWR duty.) Legislation.gov.uk
Consumer units / DBs in general spaces: Where boards are not in restricted rooms (e.g., riser cupboards serving common parts), lean on EAWR 15 + manufacturer’s instructions for safe working space and isolation reach; avoid inventing numeric “working depth” unless the OEM specifies one. Legislation.gov.ukIET Electrical
However, in dwellings, advice on mounting height for equipment not intended for regular user interaction (like meter cupboards, consumer units or router, etc.)
“Reasonable provision should be made to ensure that the approach route to any communal facilities that serve the dwelling meets these provisions. Communal facilities include storage areas, such as those used for depositing refuse and recycling, but not plant rooms or other service areas unless occupants need regular access, for example for meter reading.” ADM Section 2A Clause 2.4
“Consumer units are mounted so that the switches are 1350-1450mm above floor level” ADM Clause 1.18
3. Access during maintenance (doors/withdrawable gear)
Maintain a minimum passing width of 700 mm in use. Where doors can be fixed open or circuit-breakers are fully withdrawn, keep ≥ 500 mm to the opposite limitation.
4. Length, exits and door geometry
Gangways > 10 m shall be accessible from both ends; closed restricted‑access areas > 20 m shall be accessible by doors from both ends. Doors/hinged panels shall open to ≥ 90°.”
“Doors giving access to closed restricted areas must allow evacuation to the outside without the use of a key or tool, and gangways must allow equipment doors/panels to open to ≥ 90°. (Outward opening is strongly recommended and often adopted to facilitate evacuation.)”
5. Where “1 m clearance” comes from
credit: Dan Oxford
The Water Industry Mechanical and Electrical Specifications WIMES 3.02 Low Voltage Electrical Installations extends the BS7671 access requirement to 1000mm
“The minimum distance specified for the width of a maintenance gangway in Section 729 of BS 7671 is 700 mm, however, extending this to 1000 mm in this Specification is considered a reasonable measure to facilitate all foreseeable Assembly installation, operation and maintenance activities.” WIMES 3.02 – Low Voltage Electrical Installations Clause 3.3.5
Manufacturer’s instructions
The selection/erection must take account of manufacturer’s instructions. If an OEM or specification calls for ≥ 1000 mm frontal working depth, that becomes the project requirement over and above the 700 mm minimum, for example : https://www.se.com/uk/en/faqs/FA32222/
6. Firefighting access (layout coordination)
Provide reasonable facilities to assist fire-fighters and reasonable provision within the site for fire appliance access. Use this to coordinate plant-room locations, switchgear access routes and external yard clearances with ADB B5. GOV.UK
For small buildings: provide access to the lesser of 15% of perimeter or within 45 m of every footprint point.
Each accessible elevation to have doors at ≤ 60 m spacing (min 750 mm wide).
clause 15.3. GOV.UK
7. Practical layout rules
Step 1 — Classify the space
Restricted-access electrical rooms/areas (switchrooms, risers, plant decks; skilled/instructed persons only): apply BS 7671 Section 729 for operating/maintenance gangways and working space (plus OEM instructions).
General access areas: default to EAWR Reg. 15 (adequate working space, access and lighting) and HSG85 safe-working guidance. Legislation.gov.ukHSE
Step 2 — Overlay Part M correctly
Dwellings (Volume 1): where Part M applies, keep wall-mounted switches/sockets within 450–1200 mm A.F.L., and mount consumer unit switches 1350–1450 mm A.F.L. (Diagram 1.5). GOV.UK
Buildings other than dwellings (Volume 2): apply the accessibility objectives in user-facing spaces. But: Requirement M1 does not apply to any part of a building used solely to enable the building or any service or fitting to be inspected, repaired or maintained — i.e., plant rooms/risers aren’t Part M spaces. Use EAWR/HSG85 + BS 7671/OEM there. GOV.UK
Step 3 — Overlay manufacturer & client/sector specs
If the OEM asks for >700 mm or a specific service envelope (e.g., to withdraw ACBs), use that (BS 7671 510.3 principle).
If the client/sector has a standard (e.g., WIMES in the water industry specifying ~1 m around LV assemblies), adopt it as a project requirement.
Step 4 — Egress & doors during maintenance
Maintain safe egress while panels/doors are open. Keep a usable passing width with doors/panels at ≥90° and plan working space so operatives aren’t forced into live zones. (Use your BS 7671 Section 729 logic for restricted rooms and OEM service envelopes for each assembly.)
Two-way access for long line-ups. Where gangways are long or end-blocked by withdrawable gear, provide access from both ends (apply your Section 729 criteria).
Fire service access (ADB overlay). Where relevant to the plant location, check external door spacing/widths to support FRS access/egress.
If your client/sector adopts WIMES 3.02 (water industry): treat ~1 m clearance around LV assemblies as a hard constraint to allow:
full door opening and safe operator stance,
withdrawal of ACBs/draw-out units for routine maintenance,
a clear emergency escape route in front of the assembly.
Show the 1 m envelope on GAs/elevations, keep it free of other services/cable ladders, and reference it in your room data sheet/spec. (WIMES is a client/sector specification, not legislation—apply where the project requires it; thanks to Dan Oxford for flagging this nuance.)
Step 5 — Record the rationale (CDM)
In the design risk register/spec: state the room classification, the rule-set applied (EAWR/HSG85/BS 7671/Part M/OEM/WIMES), how evacuation is maintained during maintenance, and show removal routes for heavy components.
3 responses
Your blog is a true hidden gem on the internet. Keep up the excellent work!
Hey Jarek, just reading your latest post about clearance rules.
Your 100% correct you won’t find a blanket 1,000 mm clearance rule written into UK legislation or BS 7671 as far as I’m aware.
Exactly as you said, Legislation / ADB / HSG85 / CDM all talk about providing safe access, safe working space, and designing out maintenance risks, but none of them give a fixed measurement.
My work is mainly in the water industry, and this is where the 1 m clearance does appear – but only in sector or client specifications, not in the regs. The water industry standard WIMES 3.02 calls for 1 m clearance around LV assemblies so you can open doors properly, withdraw ACBs for normal operation and maintenance, and provide safe escape in an emergency.
Let me know if you find anything.
Thanks,
Dan
Thanks, Dan — really appreciate you sharing the water-industry context. I’ve updated the post thanks to you.